scholarly journals Monitoring Inflow Dynamics in a Multipurpose Dam Based on Travel-Time Principle

2021 ◽  
Author(s):  
Mohamad Basel Al Sawaf ◽  
kiyosi Kawanisi ◽  
Cong Xiao ◽  
Gillang Noor ◽  
Faruq Khadami ◽  
...  
Keyword(s):  
Travel Time ◽  
Management Practices ◽  
Sound Propagation ◽  
Flow Direction ◽  
Slow Flow ◽  
The Novel ◽  
Flow Environment ◽  
Dam Operation ◽  
Dam Inflow ◽  
Acoustic Travel Time

Abstract Understanding inflow dynamics in a dam lake forms the basis for optimal dam operation and management practices. However, methods pertaining to adequately determining negative inflows and addressing them, as well as quantifying uncertainties in dam inflow, have been scarcely investigated. In this study, the inflow was observed using two pairs of fluvial acoustic tomography (FAT) systems placed diagonally in a dam lake, forming a crossed-shaped pattern. The “travel-time” principle is the primary approach for measuring the inflow by FAT. The novelty of this study is in discussing the inflow characteristics within a slow water-flow environment monitored by FAT. Based on the reciprocal sound transmission, we upgraded an equation to estimate the flow direction; this newly proposed generalized equation can be used in a fluctuating flow environment. We also discussed the sound propagation characteristics for slow flow velocities. Finally, we demonstrated that a small inaccuracy in the acoustic signal, even by a sub-millisecond, can cause significant errors in measurements. One of the novel findings of this study is the detection of internal waves using the improved flow direction equation and acoustic travel-time records. Overall, this study presents a promising approach for inflow measurements under extremely slow flow conditions.

Three-Dimensional Acoustic Travel-Time Tomography of the Atmosphere

2008 ◽  
Vol 94 (3) ◽  
pp. 349-358 ◽  
Author(s):  
Sergey N. Vecherin ◽  
Vladimir E. Ostashev ◽  
Keith D. Wilson
Keyword(s):  
Travel Time ◽  
Three Dimensional ◽  
Travel Time Tomography ◽  
Acoustic Travel Time

scholarly journals Global characteristics of auroral Hall currents derived from the Swarm constellation: dependences on season and IMF orientation

2017 ◽  
Vol 35 (6) ◽  
pp. 1249-1268 ◽  
Author(s):  
Tao Huang ◽  
Hermann Lühr ◽  
Hui Wang
Keyword(s):  
Magnetic Field ◽  
Hall Current ◽  
Flow Direction ◽  
Magnetic Activity ◽  
The Novel ◽  
Polar Cap ◽  
Magnetic Field Data ◽  
Electrojet Current ◽  
Wind Input ◽  
The Imf

Abstract. On the basis of field-aligned currents (FACs) and Hall currents derived from high-resolution magnetic field data of the Swarm constellation, the average characteristics of these two current systems in the auroral regions are comprehensively investigated by statistical methods. This is the first study considering both current types determined simultaneously by the same spacecraft in both hemispheres. The FAC distribution, derived from the novel Swarm dual-spacecraft approach, reveals the well-known features of Region 1 (R1) and Region 2 (R2) FACs. At high latitudes, Region 0 (R0) FACs appear on the dayside. Their flow direction, up or down, depends on the orientation of the interplanetary magnetic field (IMF) By component. Of particular interest is the distribution of auroral Hall currents. The prominent auroral electrojets are found to be closely controlled by the solar wind input, but we find no dependence of their intensity on the IMF By orientation. The eastward electrojet is about 1.5 times stronger in local summer than in winter. Conversely, the westward electrojet shows less dependence on season. As to higher latitudes, part of the electrojet current is closed over the polar cap. Here the seasonal variation of conductivity mainly controls the current density. During local summer of the Northern Hemisphere, there is a clear channeling of return currents over the polar cap. For positive (negative) IMF By a dominant eastward (westward) Hall current circuit is formed from the afternoon (morning) electrojet towards the dawn side (dusk side) polar cap return current. The direction of polar cap Hall currents in the noon sector depends directly on the orientation of the IMF By. This is true for both signs of the IMF Bz component. Comparable Hall current distributions can be observed in the Southern Hemisphere but for opposite IMF By signs. Around the midnight sector the westward substorm electrojet is dominating. As expected, it is highly dependent on magnetic activity, but it shows only little response to season and IMF By polarity. An important finding is that all the IMF By dependences of FACs and Hall currents practically disappear in the dark winter hemisphere.

Acoustic travel time and intensity fluctuations measured in the SWARM95 experiment

1997 ◽  
Vol 101 (5) ◽  
pp. 3016-3016 ◽  
Author(s):  
Robert H. Headrick ◽  
James F. Lynch ◽  
Marshall Orr ◽  
Bruce Pasewark ◽  
Steve Wolf ◽  
...  
Keyword(s):  
Travel Time ◽  
Intensity Fluctuations ◽  
Acoustic Travel Time

Mean areal rainfall improvement using radar rainfall estimation technique by considering geographic character for dam operation

2020 ◽  
Author(s):  
Seongsim Yoon ◽  
Hongjoon Shin ◽  
Gian Choi
Keyword(s):  
Nuclear Power ◽  
Heavy Rainfall ◽  
Mountainous Area ◽  
Accuracy Improvement ◽  
Radar Rainfall ◽  
Rain Gauges ◽  
Dam Operation ◽  
Areal Precipitation ◽  
Areal Rainfall ◽  
Dam Inflow

<p>Efficiently dam operation is necessary to secure water resources and to respond to floods. For the dam operation, the amount of dam inflow should be accurately calculate. Rainfall information is important for the amount of dam inflow estimation and prediction therefore rainfall should be observed accurately. However, it is difficult to observe the rainfall due to poor density of rain gauges because of the dam is located in the mountainous region. Moreover, ground raingauges are limitted to localized heavy rainfall, which is increasing in frequency due to climate changes. The advantage of radar is that it can obtain high-resolution grid rainfall data because radar can observe the spatial distribution of rainfall. The radar rainfall are less accurate than ground gauge data. For the accuracy improvement of radar rainfall, many adjustment methods using ground gauges, have been suggested. For dam basin, because the density of ground gauge is low, there are limitations when apply the bias adjustment methods. Especially, the localized heavy rainfall occurred in the mountainous area depending on the topography. In this study, we will develop a radar rainfall adjustment method considering the orographic effect. The method considers the elevation to obtain kriged rainfall and apply conditional merging skill for the accuracy improvement of the radar rainfall. Based on this method, we are going to estimate the mean areal precipitation for hydropower dam basin. And, we will compare and evaluate the results of various adjustment methods in term of mean areal precipitation and dam inflow.</p><p>This work was supported by KOREA HYDRO & NUCLEAR POWER CO., LTD (No. 2018-Tech-20)</p><div> </div><div> </div>

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